# US 2022/0033283 A1 · Method for producing zero-valent metals in filtering media

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- Number: US 2022/0033283 A1
- Document ID: US20220033283A1
- Status: Published application
- Kind: A1
- Application number: 17/280,206
- Filed: 2019-10-11
- Published: 2022-02-03
- Earliest claimed: 2018-10-26
- Assignees: Politecnico Di Torino
- Applicants: Politecnico Di Torino
- Inventors: Rajandrea SETHI; Carlo BIANCO; Andrea GALLO; Tiziana Anna Elisabetta TOSCO
- Web page: https://patentgrep.com/patent/US20220033283A1

## CPC

- B22F 9/24: starting from liquid metal compounds, e.g. solutions
- B01D 15/206: {Packing or coating}
- B22F 1/056: {Submicron particles having a size above 100 nm up to 300 nm}
- B22F 7/08: with one or more parts not made from powder {(B22F7/062 takes precedence)}
- C02F 1/288: {using composite sorbents, e.g. coated, impregnated, multi-layered}
- C02F 1/48: with magnetic or electric fields (C02F1/46 takes precedence)
- C02F 1/705: {Reduction by metals}
- B22F 7/06: of composite workpieces or articles from parts, e.g. to form tipped tools {(B22F7/002 takes precedence)}
- B22F 2304/05: Submicron size particles
- B22F 2998/10: Processes characterised by the sequence of their steps
- C01P 2002/85: by XPS, EDX or EDAX data
- C02F 1/281: {using inorganic sorbents}
- C02F 2101/308: {Dyes; Colorants; Fluorescent agents}
- C02F 2305/08: Nanoparticles or nanotubes
- C22C 5/00: Alloys based on noble metals
- B22F: WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER (making alloys by powder metallurgy C22C); APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28)
- C02F: TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE (separation in general B01D; special arrangements on waterborne vessels of installations for treating water, waste water or sewage, e.g. for producing fresh water, B63J; adding materials to water to prevent corrosion C23F; treating radioactively-contaminated liquids G21F9/04; regeneration of reactants for recirculation into processes, see the relevant places for the processes)
- C01P: INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C22C: ALLOYS (treatment of alloys C21D, C22F)

## Abstract

A method for producing microparticles and/or nanoparticles based on zero-valent metals directly inside a filtering media and/or for creating covering layers based on the zero-valent metals for covering. The filleting media includes the steps of introducing at least one solution containing metal salts in the filtering medium, introducing at least one solution containing inorganic reducing agents into the filtering medium. The steps of introducing the at least one solution containing metal salts and the at least one solution containing inorganic reducing agents inside the filtering medium is carried out in a way separated in time and/or in space to realize, in the filtering medium, a mixture of metal ions with the inorganic reducing agents as well as a chemical reduction of the zero-valent metals to form the microparticles and/or the nanoparticles and/or coverings based on the zero-valent metals inside of the filtering medium.

## Claims

### Claim 1

A method for producing microparticles and/or nanoparticles and/or coverings containing at least one zero-valent metal inside a filtering medium, comprising the following steps:
step 100) providing a first aqueous solution of at least one metal or a salt of the at least one metal;
step 101) providing a second aqueous solution of at least one inorganic reducing agent;
step 102) preparing the filtering medium for introducing the first aqueous solution of the step 101 and the second aqueous solution of the step 102;
step 103a) introducing the first aqueous solution inside the filtering medium;
step 103b) introducing the second aqueous solution inside the filtering medium;
step 103) amounts of the first aqueous solution of the step 103a and the second aqueous solution of the step 103b are in a predetermined mutual ratio;
step 104) allowing or inducing a mixing of the first aqueous solution with the second aqueous solution inside the filtering medium in order to produce the microparticles and/or the nanoparticles and/or the coverings containing the at least one zero-valent metal (D) directly inside the filtering medium, thus modifying mechanical and/or electrical and/or chemical and/or chemical-physical and/or microbiological and/or hydrodynamic and/or geochemical and/or geotechnical and/or thermal and/or morphological and/or superficial properties of the filtering medium.

### Claim 2

A method for producing microparticles and/or nanoparticles and/or coverings containing at least one zero-valent metal inside a filtering medium, comprising the following steps:
step 201) providing a second aqueous solution of at least one inorganic reducing agent;
step 202) providing the filtering medium containing at least one metal or salt of the at least one metal, in a dissolved phase and/or a solid phase, and/or containing a fluid inside the filtering medium, static or flowing, having a non-zero concentration of the at least one metal present as the dissolved phase and/or the solid phase;
step 203) introducing the second aqueous solution inside the filtering medium;
step 204) allowing or inducing a mixing, inside the filtering medium, of the second aqueous solution with the at least one metal present in the filtering medium or in the fluid contained in the filtering medium, in order to produce the microparticles and/or the nanoparticles and/or the coverings containing the at least one zero-valent metal directly inside the filtering medium, thus modifying mechanical and/or electrical and/or chemical and/or chemical-physical and/or microbiological and/or hydrodynamic properties and/or geochemical and/or geotechnical and/or thermal and/or morphological and/or superficial properties of the filtering medium.

### Claim 3

A method for modifying mechanical and/or electrical and/or chemical and/or chemical-physical and/or microbiological and/or hydrodynamic and/or geochemical and/or geotechnical and/or superficial properties of a filtering medium and/or of a fluid, static or flowing, contained in the filtering medium, comprising a production, inside the filtering medium, of microparticles and/or nanoparticles and/or coverings of the filtering medium, containing at least one zero-valent metal by means of an introduction of a first aqueous solution of at least one metal inside the filtering medium and an introduction of a second aqueous solution of at least one inorganic reducing agent inside the filtering medium.

### Claim 4

A method for remediation and/or a treatment of a filtering medium, wherein the filtering medium is a contaminated filtering medium and/or a remediation and/or a treatment of a contaminated fluid present inside the filtering medium, comprising the steps of:
step 300) providing a first aqueous solution of at least one metal or a salt of the at least one metal;
step 301) providing a second aqueous solution of at least one inorganic reducing agent;
step 302) preparing the contaminated filtering medium for an introduction of the first aqueous solution of the step 300 and the second aqueous solution of the step 301;
step 303a) introducing the first aqueous solution into the contaminated filtering medium;
step 303b) introducing the second aqueous solution into the contaminated filtering medium;
wherein amounts of the first aqueous solution of the step 303a and the second aqueous solution of the step 303b are in a predetermined mutual ratio;
step 304) allowing or inducing a mixing, inside the contaminated filtering medium, of the first aqueous solution and a mixing, inside the contaminated filtering medium, of the second aqueous solution in order to produce microparticles and/or nanoparticles and/or coverings containing at least one zero-valent metal directly inside the contaminated filtering medium and/or to induce a reduction to a zero-valent, form of metals present on a surface of the filtering medium and/or the microparticles and/or the nanoparticles and/or the coverings containing the at least one zero-valent metal part of a solid matrix of the filtering medium and/or microparticles and/or the nanoparticles and/or the coverings containing the at least one zero-valent metal contained inside the fluid;
step 305) allowing or inducing a contact between contaminants and the microparticles and/or the nanoparticles and/or the coverings containing the at least one zero-valent metal to induce a degradation, a transformation and/or an immobilization of the contaminants.

### Claim 5 (depends on 2)

The method according to claim 2, wherein:
the fluid is flowing through the filtering medium in a natural flow or a forced flow, continuous or variable in time;
the introduction of the first aqueous solution inside the filtering medium is carried out without interrupting a bottom flow of the fluid by keeping the filtering medium always in a flow;
the introduction of the second aqueous solution inside the filtering medium is carded out without interrupting a bottom flow rate of the fluid by keeping the filtering medium always in the flow;
a generation of the microparticles and/or the nanoparticles and/or the coverings containing the at least one zero-valent metal further modifies mechanical and/or rheological and/or the chemical and/or the chemical-physical and/or toxicological and/or organoleptic and/or the microbiological and/or the geochemical properties of the fluid flowing through the filtering medium.

### Claim 6 (depends on 2)

The method according to claim 2, wherein at least one step is carried out in a presence of an electric field applied to the filtering medium and/or to the fluid contained inside the filtering medium.

### Claim 7 (depends on 6)

The method according to claim 6, wherein:
the electric field is applied to the filtering medium and/or to the fluid contained inside the filtering medium by at least two electrodes wherein the at least two electrodes are introduced inside the filtering medium or are installed in correspondence with physical points of introduction of reagents and/or coincide with the physical points or are produced directly inside the filtering medium by a localized introduction of conductive materials;
the electric field is applied imposing a current or a potential to the at least two electrodes in order to guarantee a current density inside the filtering medium in a range 0.0001 A/cm2 and 1,000 A/cm2 and an electric potential gradient in a range 0.0001 V/m and 1,000 V/m.

### Claim 8 (depends on 7)

The method according to claim 7, wherein an electric polarity at the at least two electrodes is inverted in time and/or in space.

### Claim 9 (depends on 1)

The method according to claim 1, wherein the filtering medium is selected from a porous media, a low-permeability porous media, silts, clays, a granular media, a fractured media, porous or filtering systems, structured packings and packed systems, systems of pores and/or channels and/or mutual interconnected chambers, sponges, nets and lattice systems, honeycomb-like elements, filters, fabrics, foams and foam materials, biological filters, systems allowing a filtration and/or an infiltration and/or a permeation and/or a transport of fluids internally thereof.

### Claim 10 (depends on 1)

The method according to claim 1, wherein the microparticles and/or the nanoparticles and/or the coverings produced in the filtering medium comprising a content of the at least one metal at a zero-valent state equal to at least 0.5% by weight.

### Claim 11 (depends on 4)

The method according to claim 4, wherein the microparticles and/or the nanoparticles produced in the filtering medium partly adhere to the surface of the filtering medium and are partly free to migrate through the filtering medium and/or inside the fluid.

### Claim 12 (depends on 2)

The method according to claim 2, wherein the fluid is a gas, a vapor, a liquid, the fluid further consisting of several mutual miscible or non-miscible phases, a solution, a liquid or solid aerosol, a foam, an emulsion, a sol or a mixture of the sol.

### Claim 13 (depends on 1)

The method according to claim 1, wherein the at least one metal or the salt of the at least one metal is selected from noble metals, transition metals, lanthanides, actinides or a mixture of the actinides.

### Claim 14 (depends on 13)

The method according to claim 13, wherein the at least one metal or the salt of the at least one metal is selected from silver, gold, platinum, palladium, copper, iron, manganese, zinc, nickel, indium, or a mixture of the silver, the gold, the platinum, the palladium, the copper, the iron, the manganese, the zinc, the nickel, the indium.

### Claim 15 (depends on 1)

The method according to claim 1, wherein a concentration of the at least one metal or the salt of the at least one metal is between 0.001 mM and 1 M.

### Claim 16 (depends on 15)

The method according to claim 15, wherein the concentration of the at least one metal or the salt of the at least one metal is between 1 mM and 1 M.

### Claim 17 (depends on 4)

The method according to claim 4, wherein the at least one inorganic reducing agent is selected from borohydrides, diboranes, sulfates, sulfites, bisulfites, metabisulfites, dithionites, dithionates, thiosulfates, iodides, stannous chloride, or of a mixture thereof.

### Claim 18 (depends on 17)

The method according to claim 17, wherein a mass of the at least one inorganic reducing agent in the second aqueous solution is greater than 0.001 times a stoichiometric amount necessary for a reduction reaction to the zero-valent form of the at least one metal or the salt of the at least one metal.

### Claim 19 (depends on 18)

The method according to claim 18, wherein the mass of the at least one inorganic reducing agent in the second aqueous solution is between 0.1 and 50 times the stoichiometric amount necessary for the reduction reaction to the zero-valent form of the at least one metal or the salt of the at least one metal.

### Claim 20 (depends on 1)

The method according to claim 1, wherein the second solution has a pH value between 3 and 14.

### Claim 21 (depends on 20)

The method according to claim 20, wherein the second solution has a pH value between 8 and 12.

### Claim 22 (depends on 1)

The method according to claim 1, wherein the microparticles and/or the nanoparticles and/or the coverings containing the at least one zero-valent metal produced in the filtering medium have at least one of the following characteristics:
the microparticles and/or the nanoparticles and/or the coverings containing the at least one zero-valent metal produced in the filtering medium are multimetal;
the microparticles and/or the nanoparticles and/or the coverings containing the at least one zero-valent metal produced in the filtering medium contain oxides of noble metals and/or transition metals and/or lanthanides and/or actinides; and
the microparticles and/or the nanoparticles and/or the coverings containing the at least one zero-valent metal produced in the filtering medium are embedded in a crystalline or an amorphous matrix of sulfides or sulfites or sulfates or borates of the noble metals and/or the transition metals and/or the lanthanides and/or the actinides.

### Claim 23 (depends on 1)

The method according to claim 1, wherein the first aqueous solution of the at least one metal or the salt of the at least one metal and the second aqueous solution of the at least one inorganic reducing agent are mixed before or during the introduction inside the filtering medium and the steps 103a and 103b.

### Claim 24 (depends on 1)

The method according to claim 1, wherein:
the step 103 further comprises a substep 103c wherein a third aqueous solution of the at least one metal or the salt of the at least one metal or the third aqueous solution of at least one inorganic reducing agent, with a concentration of the at least one metal or the salt of the at least one metal different from a concentration of the first aqueous solution and a concentration of the at least one inorganic reducing agent different from a concentration of the second aqueous solution, is introduced inside the filtering medium between the steps 103a and 103b to control a portion of the filtering medium, wherein the microparticles and/or the nanoparticles and/or the coverings containing the zero-valent metals are produced in the filtering medium;

### Claim 25 (depends on 24)

The method according to claim 24, wherein the third aqueous solution is water.

### Claim 26 (depends on 25)

The method according to claim 25, wherein the aqueous first solution, the second aqueous solution and/or the third aqueous solution, contain one or more stabilizing agents and/or thickeners, wherein the thickeners are organic and/or inorganic polymers, surfactants and/or polyelectrolytes.

### Claim 27 (depends on 24)

The method according to claim 24, wherein introduction modes and the amounts of the first aqueous solution, of the second aqueous solution and of the third aqueous solution concentrations of the at least one metal or the salt of the at least one metal and/or of the at least one inorganic reducing agent, flow rates applied, a duration and an order of individual steps are predetermined to control a portion of the filtering medium, wherein the microparticles and/or the nanoparticles and/or the coverings containing the zero-valent metals are produced.

### Claim 28 (depends on 24)

The method according to claim 24, wherein the step 103 and substeps 103a, 103b and 103c are cyclically repeated.

### Claim 29 (depends on 2)

The method according to claim 2, wherein the step 203 is cyclically repeated.

### Claim 30 (depends on 28)

The method according to claim 28, wherein, between one cycle and a next cycle, the third aqueous solution is introduced inside the filtering medium.

### Claim 31 (depends on 24)

The method according to claim 24, wherein the step 103 and substeps 103a, 103b and 103c, are cyclically repeated with different operating modes or by varying an order of the substeps, using different metals and/or reducing agents and/or using different physical points and different times of introduction.

### Claim 32 (depends on 28)

The method according to claim 28, wherein the step 103 and substeps thereof 103a, 103b and 103c are cyclically repeated alternating in each cycle a use of a noble metal and of a transition metal or a metal belonging to a group of lanthanides or actinides.

### Claim 33 (depends on 1)

The method according to claim 1, when wherein a concentration of the at least one metal in the first aqueous solution is lower than 0.1 mM.

### Claim 34 (depends on 24)

The method according to claim 24, wherein the introduction, inside the filtering medium, of the at least one metal or the salt of the at least one metal, the introduction, inside the filtering medium, of the at least one inorganic reducing agent, and the introduction, inside the filtering mediumm, of the third aqueous solution, takes place according to one of the following modes:
sequentially, with introduction steps occurring at different times, from a same introduction point or from different introduction points;
at the same time, at different points in space; and
at the same introduction point, but at different levels or depths.

### Claim 35 (depends on 1)

The method according to claim 1, wherein the mixing between the at least one metal or the salt of the at least one metal and the at least one inorganic reducing agent takes place directly inside the filtering medium through at least one of the following mechanisms:
a velocity difference in the filtering medium, delayed transport of the at least one metal or the delayed transport of the at least one reducing agent, a viscous fingering, a chaotic convection, a density difference, a hydrodynamic dispersion, temperature and/or viscosity and/or density and/or phase contrasts, an electrophoresis, an electrokinetics, an electrosmosis, a generation of electric, magnetic or electromagnetic fields, different solubility of the at least one metal or different solubility of the at least one reducing agent, application of ultrasounds, and/or an alternate pumping and/or a suction and a re-injection, a local inversion of a flow direction and/or exploitation of natural or induced heterogeneities of an hydraulic conductivity and/or other hydrodynamic properties of the filtering medium or of a saturation of the filtering medium.

### Claim 36 (depends on 2)

The method according to claim 2, wherein the filtering medium contains the at least one metal or the salt of the at least one metal, in the dissolved phase and/or the solid phase, and/or contains a fluid inside the filtering medium, static or in flow, having the non-zero concentration of the at least one metal in the dissolved phase and/or the solid phase.

### Claim 37 (depends on 24)

The method according to claim 24, wherein the filtering medium (C) is a soil and/or a subsoil, and a unsaturated medium, or a vadose zone, or a capillary fringe or aquifer systems, both artesian and phreatic, or a combination the artesian and phreatic, or wherein the filtering medium is a portion of the soil and/or the subsoil extracted and prepared on purpose for an introduction of the at least one metal or the salt of the at least one metal an introduction of the at least one reducing agent, and an introduction of the third aqueous solution.

### Claim 38 (depends on 2)

The method according to claim 2, wherein the filtering medium and/or the fluid contained in the filtering medium are contaminated or potentially contaminated.

### Claim 39 (depends on 1)

The method according to claim 1, wherein the at least one metal or the salt of the at least one metal, the at least one reducing agent and the third aqueous solution, are introduced inside the filtering medium through at least one of the following introduction techniques:
injection through individual wells;
injection through multilevel wells;
a direct push;
mixing with a subsoil;
mixing with a subsoil;
trenches;
dosing at a campaign level;
application of a positive pressure, by a suction or by an effect of gravity only;
fracturing of the filtering medium or a permeation; and
in any other mode suitable to deliver materials in the subsoil or by a combined use of introduction techniques.